The present invention is related to supports for movably holding a board or other workpiece and more particularly to such supports that will allow multidirectional motion of the board.
Floor-supported woodworking tools typically include a workpiece support "table" and a stationary "fence" or guide that is used to direct boards in a defined path past a woodworking station. Practicality and space requirements dictate the dimension of the guide and support table, which is typically too small for handling large workpieces. Additional support is required for accurate, safe work, with long boards or large workpieces such as plywood.
Various auxiliary supports for large or elongated workpieces have been designed in the past. An example of a portable support of this nature is disclosed in U.S. Pat. No. 4,039,064 to R. Kirby. The Kirby support can be moved easily from one work area to another and can be easily adjusted to various working heights. However, the unit will operate only while under certain working conditions--when the workpiece is to be moved in a direction perpendicular to the roller axis. The roller will rotate beneath the workpiece but will slide frictionally when the direction of the workpiece movement is other than perpendicular to the roller axis. In circumstances such as during board ripping operations, this feature is desirable. However, there remains a need for an inexpensive universal type support that will allow motion of a board or a workpiece in a variety of directions.
U.S. Pat. No. 2,818,092 to L. E. Grosset discloses a universal work support in which a plurality of "caster wheels" are mounted along a bar and held on an adjustable stand with the wheels inverted and projecting upwardly. The caster wheels allow a certain "universal" motion of the workpiece but can also cause light shifting of the workpiece when the casters pivot about the axes of their mounting shafts. Such slight motion could result in an inaccurate pass of the workpiece and, furthermore, could result in binding between the workpiece and the associated machine.
U.S. Pat. No. 1,251,881 to W. N. Goodwin describes a skid that uses spherical rollers in place of casters. The rollers project beyond a race to engage the workpiece. The race is formed in two halves, each having a semispherical recess for journalling a roller. Only a small portion of each roller projects beyond the race. The remainder of the roller periphery is engaged by the race. Accumulation of dust or other foreign material between the rollers and race could therefore hamper free rotation of the rollers. Frequent cleaning would become necessary and each roller must then be removed so each recess could be cleaned separately. The process could become more complicated when several rollers are involved.
Other U.S. patents, specifically U.S. Pat. Nos. 4,060,252; 3,559,802; and 1,963,596 all disclose "transfer" apparatus using semispherical or similar roller receiving recesses for journalling spherical rollers. These disclosures therefore show the same cleanout problem that would be experienced with the Goodwin device if used as a multidirectional board support.
The present invention makes use of a base having upright intersecting ribs that include semicyclindrical recesses at the intersections thereof. Spaces between the intersecting ribs allow dust and debris to fall free of the rollers. This material can then be periodically removed without requiring removal of the rollers from their cradles. There are no "sockets" that must be individually cleaned after removal of the associated roller. The base and rollers are selectively covered primarily to prevent escape of the rollers from their cradles and secondarily to avoid accumulation of debris, since cleanout may be accomplished quickly and effectively.